Quartz glass pinch seal of increased compressive strength

ABSTRACT

An electric incandescent lamp of the halogen type including an envelope of quartz glass having an external press seal composed of a flat mid-section limited by two plane parallel faces and two flanges extending parallel to the lamp axis and enclosing the mid-section so that the cross section of the seal in a plane perpendicular to the lamp axis is of I-shape. The lamp is provided with leads sealed into the press seal in the form of metal foil seals with outer lead wires protruding from the bottom end of the press seal as base contacts and including in the press seal, where it merges with the envelope body, a transverse depression or corrugation extending across substantially the entire width of the press seal.

United States Patent 11 1 Stadler 1 Dec 18, 1973 1 1 QUARTZ GLASS PINCHSEAL OF FOREIGN PATENTS OR APPLICATIONS INCREASED COMPRESSIVE STRENGTH1,214,736 12/1970 Great Britain 313/318 [75] Inventor: Karl Stadler,Rebdorf, Germany [73] Assignee: Patent-Treuhand-Gesellschaft Fur PrimaryEXami"@rDa/id Schonberg Elektrische Gluhl b I-[,, AssistantExaminer-Paul A. Sacher M i h Germany Att0rneyA. T. Stratton et a1.

[22] Filed: June 6, 1972 Appl. No.: 260,089

[ 5 7 ABSTRACT An electric incandescent lamp of the halogen typeincluding an envelope of quartz glass having an external press sealcomposed of a flat mid-section limited by two plane parallel faces andtwo flanges extending parallel to the lamp axis and enclosing themid-section so that the cross section of the seal in a planeperpendicular to the lamp axis is of I-shape. The lamp is provided withleads sealed into the press seal in the form of metal foil seals withouter lead wires protruding from the bottom end of the press seal asbase contacts and including in the press seal, where it merges with theenvelope body, a transverse depression or corrugation extending acrosssubstantially the entire width of the press seal.

4 Claims, 3 Drawing Figures PAIENTEUHEB 18 ms FIG.2.

FIG.I.'

QUARTZ GLASS PINCH SEAL OF INCREASED COMPRESSIVE STRENGTH BACKGROUND OFTHE INVENTION The conventional halogen type incandescent lamp includesan envelope of quartz glass and an external press seal designed toconstitute the base. The leads for the lamp are sealed into the pressseal in the form of foils and outer lead wires protrude at the bottomend as base contacts and the inner lead wires extend into the envelopespace and are connected to the lamp filament. In a quartz press seal ofthis type, bursting or leakage of the lamp at the end of its useful lifefrequently occurs due to lack of compressive strength at the seal. Inorder to avoid this burstingor leakage, various alternative steps havebeen taken. Primarily, these steps have included efforts to adjust thepinching and the burners, in order to obtain an increased compressivestrength at the seal. However, none of these measures has led to theproduction of a satisfactory press seal which is free from the aforesaiddeleterious bursting or leakage problems as the lamp approaches the endof its useful life.

SUMMARY OF THE INVENTION The above described drawbacks have beenobviated by providing in an electric incandescent lamp comprising alight transmitting envelope body having an external press seal at leastat one end thereof, and a pair of foil type lead-in conductors sealedtherein and connected within said envelope to a filament; theimprovement which comprises a transverse depression extending across thepress seal adjacent the juncture of the pressseal with the envelope bodyto thereby provide an area of substantially increased cold compressivestrength to said press seal.

BRIEF DESCRIPTION OF THE DRAWINGS The many attendant advantages of thisinvention will become more readily apparent and better understood as thefollowing detailed description is considered in connection with theaccompanying drawings, in which:

FIG. 1 is a front elevational view of an incandescent lamp constructedin accordance with this invention.

FIG. 2 is a sectional view of the pinch seal taken along the line IIIIof FIG. 1; and

FIG. 3 is a bottom end view of the pinch seal of this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now in detail to thedrawings, wherein like reference characters represent like partsthroughout the several views, there is illustrated in FIG. 1 an electricincandescent lamp of the invention generally designated 10. The lampincludes a light transmitting envelope of conventional constructionincluding the envelope portion 12 and a press seal portion 14. The pressseal is generally of I-shaped cross section perpendicular to the lampaxis as can be best seen from FIG. 3. The pinch seal is formed by amid-section l6 limited by two plane parallel faces constituting a webportion and by flanges l8 enclosing the web and extending parallel tothe lamp axis. Flanges 18 are merged via steps 20 into the web ormid-section 16 whereby the great difference in thickness between the weband flange is bridged. The lamp leads in the form of metal foils 22 aresealed into the web in combination with the inner lead wires 24 and theouter lead wires 26. The outer lead wires 26 protrude at the bottom endof the pinch seal as base contacts while the inner lead wires 24 extendinto the envelope body and have an incandescent filament 28 connectedtherebetween.

To prevent'bursting or leakage of the lamp due to lack of compressivestrength at the seal a corrugation or depression 30 extendingtransversely across'the entire web portion of the pinch seal, andlimited by the two flanges is provided. The depression or corrugation 30reduces the cross section of the web portion of the pinch seal toapproximately one-half the remaining thickness of the web portion 16 andresults in an area of increased cold compressive strength of at least 20atmospheres absolute pressure which thus prevents a bursting or leakageof the lamp. The depression or corrugation 30 may be provided by aspecially designed pinching jaw which causes the pinching pressure atthe place of corrugation or depression to be increased relative to theother portions of the press seal.

1 claim as my invention:

1. In an electric incandescent lamp comprising a light transmittingenvelope body having an external press seal at at least one end thereof,said external press seal being substantially I-shaped in cross sectionand including two plane parallel faces constituting a webb portion lyingbetween a pair of spaced parallel flange portions, and a pair of foiltype lead-in conductors sealed therein and connected in said envelope toa'filament, the improvement comprising, a transverse depressionextending across said webb portion between said flange portions adjacentthe juncture of said press seal with said envelope body.

2. An incandescent lamp according to claim 1 wherein the thickness ofsaid web portion is approximately twice the thickness at saiddepression.

3. An electric incandescent lamp of the halogen type comprising: a lampbody having an envelope and a press seal portion; a pair of outer leadwires extending into said press seal portion; a pair of inner lead wiresextending out of said press seal portion and extending into saidenvelope portion; a lamp filament connected between said inner leadwires within said envelope portion; metal foil leads connected betweensaid outer lead wires and said inner lead wires within said press seal,said press seal being substantially l-shaped in crosssection andincluding two plane parallel faces constituting a webb portion lyingbetween :a pair of spaced parallel flange portions; and a transversecorrugation extending across said webb portion between said flangeportions at a location between said foil leads and said envelopeportion, thereby providing an area of substantially increased coldcompressive strength to said press seal.

4. An electric incandescent lamp according to claim 3 wherein the crosssectional thickness of said press seal at said web portion isapproximately twice the cross sectional thickness at said corrugation.

1. In an electric incandescent lamp comprising a light transmittingenvelope body having an external press seal at at least one end thereof,said external press seal being substantially I-shaped in cross sectionand including two plane parallel faces constituting a webb portion lyingbetween a pair of spaced parallel flange portions, and a pair of foiltype leadin conductors sealed therein and connected in said envelope toa filament, the improvement comprising, a transverse depressionextending across said webb portion between said flange portions adjacentthe juncture of said press seal with said envelope body.
 2. Anincandescent lamp according to claim 1 wherein the thickness of said webportion is approximately twice the thickness at said depression.
 3. Anelectric incandescent lamp of the halogen type comprising: a lamp bodyhaving an envelope and a press seal portion; a pair of outer lead wiresextending into said press seal portion; a pair of inner lead wiresextending out of said press seal portion and extending into saidenvelope portion; a lamp filament connected between said inner leadwires within said envelope portion; metal foil leads connected betweensaid outer lead wires and said inner lead wires within said press seal,said press seal being substantially I-shaped in cross-section andincluding two plane parallel faces constituting a webb portion lyingbetween a pair of spaced parallel flange portions; and a transversecorrugation extending across said webb portion between said flangeportions at a location between said foil leads and said envelopeportion, thereby providing an area of substantially increased coldcompressive strength to said press seal.
 4. An electric incandescentlamp according to claim 3 wherein the cross sectional thickness of saidpress seal at said web portion is approximately twice the crosssectional thickness at said corrugation.